Editing T-tail

{{Short description|Aircraft empennage configuration}}
{{Refimprove|date=December 2007}}
[[File:Bae146.avrorj85.arp.750pix.jpg|thumb|[[British Aerospace 146|Avro RJ-85]] of [[SN Brussels Airlines]] (Belgium)]]
[[File:McDonnell Douglas MD-90 (Japan Airlines) d.jpg|thumb|[[McDonnell Douglas MD-90]]]]
[[File:Piper PA44-180 aircraft.jpg|thumb|Piper PA-44-180 Seminole]]
[[File:grob.g109b.glider.arp.jpg|thumb|[[Grob G 109]] [[motor glider]]]] 
[[File:beechcraft 1900d d-cbig fairford arp.jpg|thumb|[[Beechcraft 1900]]D of the [[Swiss Air Force]]]] 
[[File:T-tail en.svg|thumb|T-tail of aircraft ([[Tu-154]])]]

A '''T-tail''' is an [[empennage]] [[wikt:configuration|configuration]] in which the [[tailplane]] of an [[aircraft]] is mounted to the top of the [[vertical stabilizer|fin]]. The arrangement looks like the capital letter T, hence the name. The T-tail differs from the standard configuration in which the tailplane is mounted to the [[fuselage]] at the base of the fin.

==Advantages==

T-tails were common in early jet aircraft. Designers were worried that an engine failure would otherwise damage the horizontal tail.

The T-tail is very common on aircraft with engines mounted in [[nacelle]]s on a [[Wing_configuration#Number_and_position_of_main_planes|high-winged]] aircraft or on aircraft with the engines mounted on the rear of the fuselage, as it keeps the tail clear of the jet exhaust.{{cn|date=June 2024}} Rear-mounting the engines keeps the wings clean and improves short-field performance. This was necessary in early jet aircraft with less powerful engines.<ref name="Hush-Kit">{{cite web |title=T-time? Why Britain fell in love with the T-tailed aeroplane |url=https://hushkit.net/2020/04/05/t-time-why-britain-fell-in-love-with-the-t-tailed-aeroplane/ |website=Hush-Kit |access-date=13 October 2022 |language=en |last1=Smith |first1=Jim |date=5 April 2020}}</ref>

T-tail aircraft can have better short-field performance,<ref name="Hush-Kit"/> such as on the [[British Aerospace 146|Avro RJ-85]]. The disturbed airflow over a lower stabilizer can make control more difficult at lower speeds.{{cn|date=June 2024}}

During normal flying conditions, the tailplane of a T-tail is out of the disturbed airflow behind the [[wing]] and fuselage,<ref name="Hush-Kit"/> which provides for more consistent elevator response.{{cn|date=June 2024}}

The design and structure of a T-tail can be simpler.<ref name="Hush-Kit"/>

For a [[transsonic]] aircraft a T-tail configuration may improve pitch control effectiveness, because the elevator is not in disturbed air behind the fuselage, particularly at moderate angles of attack.{{cn|date=October 2022}}

Depending on wing location, the elevator may remain in undisturbed airflow during a [[Stall (fluid dynamics)|stall]]. (However, T-tail aircraft may be vulnerable to [[Stall (fluid dynamics)#Deep stall|deep stall]], see [[#Disadvantages|Disadvantages]] below.)

An aircraft with a T-tail may be easier to recover from a [[spin (aerodynamics)|spin]], as the elevator is not in a position to block airflow over the rudder, which would make it ineffective, as can happen if the horizontal tail is directly below the fin and rudder.<ref>{{Cite web|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005341.pdf|title=Summary of spin technology as related to light general-aviation airplanes|date=December 1971|last1=Bowman|first1=J. S.}}</ref>

The T-tail increases the effectiveness of the vertical tail because of "end plate" effect. The horizontal stabilizer acts like a winglet, reducing [[induced drag]] of the rudder.<ref name="Hoerner">Hoerner and Borst, ''Fluid Dynamic Lift'', Directional Characteristics, T-tail page 13-11</ref><ref name="Hush-Kit"/> Smaller and lighter T-tails are often used on modern gliders.

When the vertical tail is swept, the horizontal tail can be made smaller because it is further rearwards and therefore has a greater lever arm. Tail sweep may be necessary at high Mach numbers.

A T-tail may have less interference drag, such as on the [[Tupolev Tu-154]].

T-tails may be used to increase clearance at the rear of a cargo aircraft such as the [[Boeing C-17 Globemaster]], to provide extra clearance when loading the aircraft.{{cn|date=June 2024}}

T-tails decrease the possibility of anything hitting the empennage on paratroops or airdrops operations, as the tail is way above the jump door.

==Disadvantages==
The aircraft may be prone to [[Stall (fluid dynamics)#Deep stall|deep stall]] (or super stall) at high [[angles of attack]], when airflow over the tailplane and elevators is blanked by the wings.<ref>{{cite web |url=http://www.thunder-and-lightnings.co.uk/javelin/history.php|title=Gloster Javelin - History |work=Thunder & Lightnings}}</ref><ref name="Hush-Kit"/> The American [[McDonnell F-101 Voodoo]] jet fighter suffered from this problem,{{citation needed|date=February 2017}} as did the British [[Gloster Javelin]], [[Hawker Siddeley Trident]] and [[BAC One-Eleven]]. A stick-pusher can be fitted to deal with this problem.<ref name="Hush-Kit"/><ref name="Davies">{{cite book |last1=Davies |first1=David P. |title=Handling the Big Jets: An Explanation of the Significant Differences in Flying Qualities Between Jet Transport Aeroplanes and Piston Engined Transport Aeroplanes, Together with Some Other Aspects of Jet Transport Handling |date=1971 |publisher=Air Registration Board |url=https://books.google.com/books?id=TKZTAAAAMAAJ |language=en |isbn=0903083019 |edition=3rd |pages=116–118}}</ref>

For propeller aircraft, a T-tail configuration may reduce pitch control effectiveness if the elevators are outside the propeller slipstream.{{cn|date=October 2022}}

The vertical stabilizer must be made stronger (and therefore heavier) to support the weight of the tailplane.{{cn|date=June 2024}} (However other factors may make the T-tail smaller and lighter, see [[#Advantages|Advantages]] above.)

A T-tail produces a strong nose-down pitching moment in sideslip.

T-tails can cause [[Aeroelasticity|aeroelastic flutter]], as seen on the [[Lockheed C-141 Starlifter]]. The fuselage must be made stiffer to counteract this.

Many large aircraft can have the fin and rudder fold to reduce height in hangars, however this generally isn't feasible or useful if there is a T-tail.{{cn|date=October 2022}}
[[File:Gulfstream G650 departs Bristol 23rdAug2014 arp.jpg|thumb|[[Gulfstream G650/G700/G800|Gulfstream G650]] with a T-tail and [[Rear-engine jet|rear-engines]]]]
The T-tail configuration can also cause maintenance problems. The control runs to the elevators are more complex,{{cn|date=June 2024}} and the surfaces are more difficult to inspect from the ground. The loss of [[Alaska Airlines Flight 261]] was attributed to improper maintenance of the T-tail.{{citation needed|date=February 2017}} T-tails can be harder to inspect or maintain, due to their height.{{cn|date=June 2024}}

==Adoption==

The T-tail can often be found on military transport aircraft, such as the [[Airbus A400M]], the [[Boeing C-17 Globemaster III]] and the [[Embraer C-390 Millennium|Embraer C-390 Millenium]]. It was used in the 1950s by combat aircraft such as the [[Gloster Javelin]], [[McDonnell F-101 Voodoo]], and [[Lockheed F-104 Starfighter]] [[interceptor aircraft|interceptors]], and on the [[Blackburn Buccaneer]] [[attack aircraft]].

T-tails are often used on regional airliners and business aircraft, especially when rear-fuselage-mounted turbofan engines are used.  

In the 1960s, T-tails were used on the [[BAC One-Eleven]], [[Vickers VC10]], [[McDonnell Douglas DC-9]],  [[Boeing 727]], [[Fokker F28 Fellowship]], [[Ilyushin Il-62]] and [[Tupolev Tu-154]]. It has been used by the [[Gulfstream Aerospace|Gulfstream]] family since the [[Grumman Gulfstream II]]. It has been used by the [[Learjet]] family since their first aircraft, the [[Learjet 23]]. It has also been used by the Embraer's [[Embraer Phenom 100|Phenom 100]], [[Embraer Phenom 300|Phenom 300]] and [[Embraer Legacy 450/500 and Praetor 500/600|Legacy/Praetor]] business jet families.  

In the 1970s it was used on the [[McDonnell Douglas MD-80]] and [[Ilyushin Il-76]], as well as the twin turboprop [[Beechcraft Super King Air]]. In the 1980s it was used on the [[Fokker 100]] and the [[British Aerospace 146]].

In the 1990s it was used on the [[Boeing 717]], [[Bombardier CRJ|Bombardier CRJ-Series]], [[Embraer ERJ family]], [[Fokker 70]] and  [[McDonnell Douglas MD-90]], as well as the single turboprop [[Pilatus PC-12]].

T-tail is especially popular on modern [[Glider (aircraft)|glider]]s because of the high performance, the safety it provides from accidental spins, and the safety it provides the stabilizer and elevator from foreign object damage on take-off and landing.

==See also==
* [[Cruciform tail]]
* [[Pelikan tail]]
* [[Twin tail]]
* [[V-tail]]
* [[Hans Multhopp]], a pioneer user of the T-Tail concept near World War II's end

==References==
{{Reflist}}

==Further reading==
* {{cite magazine |url= https://www.flightglobal.com/pdfarchive/view/1979/1979%20-%203762.html |title= T-tails and top technology |magazine= Flight International |date= 13 Oct 1979}}

{{Aircraft components}}

[[Category:Aircraft aerodynamics]]
[[Category:Aircraft tail configurations]]